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+/*
+ * strtod.c --
+ *
+ * Source code for the "strtod" library procedure.
+ *
+ * Copyright (c) 1988-1993 The Regents of the University of California.
+ * Copyright (c) 1994 Sun Microsystems, Inc.
+ *
+ * See the file "license.terms" for information on usage and redistribution
+ * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+ *
+ * RCS: @(#) $Id$
+ */
+
+#include "config.h"
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#include <ctype.h>
+#include <errno.h>
+extern int errno;
+
+#ifndef __STDC__
+# ifdef __GNUC__
+# define const __const__
+# else
+# define const
+# endif
+#endif
+
+#ifndef TRUE
+#define TRUE 1
+#define FALSE 0
+#endif
+#ifndef NULL
+#define NULL 0
+#endif
+
+static int maxExponent = 511; /* Largest possible base 10 exponent. Any
+ * exponent larger than this will already
+ * produce underflow or overflow, so there's
+ * no need to worry about additional digits.
+ */
+static double powersOf10[] = { /* Table giving binary powers of 10. Entry */
+ 10., /* is 10^2^i. Used to convert decimal */
+ 100., /* exponents into floating-point numbers. */
+ 1.0e4,
+ 1.0e8,
+ 1.0e16,
+ 1.0e32,
+ 1.0e64,
+ 1.0e128,
+ 1.0e256
+};
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * strtod --
+ *
+ * This procedure converts a floating-point number from an ASCII
+ * decimal representation to internal double-precision format.
+ *
+ * Results:
+ * The return value is the double-precision floating-point
+ * representation of the characters in string. If endPtr isn't
+ * NULL, then *endPtr is filled in with the address of the
+ * next character after the last one that was part of the
+ * floating-point number.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+double
+strtod(string, endPtr)
+ const char *string; /* A decimal ASCII floating-point number,
+ * optionally preceded by white space.
+ * Must have form "-I.FE-X", where I is the
+ * integer part of the mantissa, F is the
+ * fractional part of the mantissa, and X
+ * is the exponent. Either of the signs
+ * may be "+", "-", or omitted. Either I
+ * or F may be omitted, or both. The decimal
+ * point isn't necessary unless F is present.
+ * The "E" may actually be an "e". E and X
+ * may both be omitted (but not just one).
+ */
+ char **endPtr; /* If non-NULL, store terminating character's
+ * address here. */
+{
+ int sign, expSign = FALSE;
+ double fraction, dblExp, *d;
+ register const char *p;
+ register int c;
+ int exp = 0; /* Exponent read from "EX" field. */
+ int fracExp = 0; /* Exponent that derives from the fractional
+ * part. Under normal circumstatnces, it is
+ * the negative of the number of digits in F.
+ * However, if I is very long, the last digits
+ * of I get dropped (otherwise a long I with a
+ * large negative exponent could cause an
+ * unnecessary overflow on I alone). In this
+ * case, fracExp is incremented one for each
+ * dropped digit. */
+ int mantSize; /* Number of digits in mantissa. */
+ int decPt; /* Number of mantissa digits BEFORE decimal
+ * point. */
+ const char *pExp; /* Temporarily holds location of exponent
+ * in string. */
+
+ /*
+ * Strip off leading blanks and check for a sign.
+ */
+
+ p = string;
+ while (isspace(*p)) {
+ p += 1;
+ }
+ if (*p == '-') {
+ sign = TRUE;
+ p += 1;
+ } else {
+ if (*p == '+') {
+ p += 1;
+ }
+ sign = FALSE;
+ }
+
+ /*
+ * Count the number of digits in the mantissa (including the decimal
+ * point), and also locate the decimal point.
+ */
+
+ decPt = -1;
+ for (mantSize = 0; ; mantSize += 1)
+ {
+ c = *p;
+ if (!isdigit(c)) {
+ if ((c != '.') || (decPt >= 0)) {
+ break;
+ }
+ decPt = mantSize;
+ }
+ p += 1;
+ }
+
+ /*
+ * Now suck up the digits in the mantissa. Use two integers to
+ * collect 9 digits each (this is faster than using floating-point).
+ * If the mantissa has more than 18 digits, ignore the extras, since
+ * they can't affect the value anyway.
+ */
+
+ pExp = p;
+ p -= mantSize;
+ if (decPt < 0) {
+ decPt = mantSize;
+ } else {
+ mantSize -= 1; /* One of the digits was the point. */
+ }
+ if (mantSize > 18) {
+ fracExp = decPt - 18;
+ mantSize = 18;
+ } else {
+ fracExp = decPt - mantSize;
+ }
+ if (mantSize == 0) {
+ fraction = 0.0;
+ p = string;
+ goto done;
+ } else {
+ int frac1, frac2;
+ frac1 = 0;
+ for ( ; mantSize > 9; mantSize -= 1)
+ {
+ c = *p;
+ p += 1;
+ if (c == '.') {
+ c = *p;
+ p += 1;
+ }
+ frac1 = 10*frac1 + (c - '0');
+ }
+ frac2 = 0;
+ for (; mantSize > 0; mantSize -= 1)
+ {
+ c = *p;
+ p += 1;
+ if (c == '.') {
+ c = *p;
+ p += 1;
+ }
+ frac2 = 10*frac2 + (c - '0');
+ }
+ fraction = (1.0e9 * frac1) + frac2;
+ }
+
+ /*
+ * Skim off the exponent.
+ */
+
+ p = pExp;
+ if ((*p == 'E') || (*p == 'e')) {
+ p += 1;
+ if (*p == '-') {
+ expSign = TRUE;
+ p += 1;
+ } else {
+ if (*p == '+') {
+ p += 1;
+ }
+ expSign = FALSE;
+ }
+ while (isdigit(*p)) {
+ exp = exp * 10 + (*p - '0');
+ p += 1;
+ }
+ }
+ if (expSign) {
+ exp = fracExp - exp;
+ } else {
+ exp = fracExp + exp;
+ }
+
+ /*
+ * Generate a floating-point number that represents the exponent.
+ * Do this by processing the exponent one bit at a time to combine
+ * many powers of 2 of 10. Then combine the exponent with the
+ * fraction.
+ */
+
+ if (exp < 0) {
+ expSign = TRUE;
+ exp = -exp;
+ } else {
+ expSign = FALSE;
+ }
+ if (exp > maxExponent) {
+ exp = maxExponent;
+ errno = ERANGE;
+ }
+ dblExp = 1.0;
+ for (d = powersOf10; exp != 0; exp >>= 1, d += 1) {
+ if (exp & 01) {
+ dblExp *= *d;
+ }
+ }
+ if (expSign) {
+ fraction /= dblExp;
+ } else {
+ fraction *= dblExp;
+ }
+
+done:
+ if (endPtr != NULL) {
+ *endPtr = (char *) p;
+ }
+
+ if (sign) {
+ return -fraction;
+ }
+ return fraction;
+}